Needle sheath remover assembly

ABSTRACT

The invention relates to a needle sheath remover comprising a cap ( 10 ) removably attached to a housing of a medicament delivery device, a sheath grabber ( 20 ) connected to said cap and configured to be engageable to a needle sheath ( 42 ) of a medicament container positioned ( 46 ) within said medicament delivery device, wherein the cap and the sheath grabber are axially movable in relation to each other and wherein the sheath grabber and the cap are configured to interact with each other such that upon removal of the cap from the housing, the sheath grabber is capable of engaging and removing said needle sheath.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/343,853 filed Mar. 9, 2014, which is a 35 U.S.C. 371National Application of PCT/SE2012/050655 filed Jun. 15, 2012, whichclaims the benefit of U.S. Provisional Patent Application No. 61/504,555which claims priority to Swedish Patent Application No. 1150630-0 filedJul. 5, 2011, the entire contents of which are incorporated entirelyherein by reference.

TECHNICAL FIELD

The present invention relates to an assembly for the safe and easyremoval of needle sheaths of medicament delivery devices.

BACKGROUND

Many medicament delivery devices on the market have been developed forself administration of medicament, where one large group is medicamentinjection devices. Many of these injection devices have been providedwith removable needle cover assemblies where the core cover is a needlesheath.

These sheaths are arranged to protect an injection needle before use inorder to keep the needle sterile and also to protect the user fromunintentional needle sticks. The sheaths are pushed onto the neckportion of a medicament container, such as a syringe or cartridge,during assembly of container, needle and sheath. The sheath ispreferably of a resilient material, normally rubber, which ensures atight grip and a good seal between the outer environment and thesyringe. However this tight grip also means that it is relativelydifficult to remove the sheath from the syringe in order to perform aninjection.

Therefore a number of sheath removal devices have been developed, whichare intended to aid the user in removing the sheath. DocumentsWO2010089589 and EP2021057 disclose different solutions to this problem.

WO2010089589 describes a device in which a housing of an autoinjectorcomprises an axially extending boss positioned to interfere with camsurfaces of axially extending fingers of a needle sheath removing means.During axial separation, the interference of the cam surfaces and theboss forces the fingers to flex radially inwards to grip a needle sheathof the autoinjector. This solution suffers the disadvantage of havingthe boss integrated with the housing, i.e. stationary, as the needlesheath moves axially in relation to the housing. If the fingers do notattain a good grip until the cam surfaces fully enter the narrow passageformed by the boss of the housing, the sheath may refuse to move and thefingers will slide. The sheath remover also risks getting stuck due totolerance mismatch which may cause passage of the boss/housing to be toonarrow for the cam surfaces to be able to enter it. Also, the proposeddesign of the autoinjector housing is very complicated to manufacture.

EP2021057 describes a cap for an injection device comprising a firstpart with a grip means for engaging the rear surface of a needle sheathat a neck portion of a medicament container. Upon assembly of the devicethe first part is attached to the front end of the injection device suchthat the grip means snap into engagement behind the needle sheath. Asecond part is subsequently attached to the first part to prevent thegrip means from disengaging the rear surface of the sheath.

To grip behind the needle sheath is difficult since tolerances fromassembling the containers and needle sheaths are not very accurate. If,during assembly of sheath, needle and container, the sheath is pushedfar onto the neck portion of the container there may not be enough roomfor the fingers of the grip means to engage behind the sheath. Also, thegrip is not very tight since it only depends on the grip means flexingradially behind the sheath and then being locked by the second part.There is no force to squeeze the sheath during removal. Therefore, sucha solution would risk losing its grip on a soft rubber needle sheath.

An added disadvantage is that as the user tries to remove the cap andthe sheath from the injection device he will have to overcome thefriction between the cap and the device as well as the friction betweenthe sheath and the needle at the same time. It may be difficult forusers with weak hands, or for users with impaired manual dexterity, toovercome the accumulated force of the two friction interfaces.

Therefore, there is a need for a device that can securely remove aneedle sheath from a needle regardless of the tolerances of thecontainer or sheath. The device should also require little strength toremove and should be simple to manufacture.

SUMMARY

According to the main aspect of the invention, it relates to a needlesheath remover assembly for use in a medicament delivery device, axiallyelongated in a proximal and a distal direction, comprising a capconfigured to be removably attached to a housing of a medicamentdelivery device, a sheath grabber connected to said cap and configuredto be engageable to a needle sheath of a medicament container positionedwithin said medicament delivery device, wherein said cap and said sheathgrabber are axially movable in relation to each other and wherein saidsheath grabber and said cap are configured to interact with each othersuch that upon removal of said cap from the housing, said sheath grabberis capable of engaging and removing said needle sheath.

According to another aspect of the invention, said sheath grabbercomprises second stop means and engaging means and wherein said capcomprises second blocking means and biasing means.

According to a further aspect of the invention, said cap is coaxiallymovable relative to the sheath grabber preferably wherein movement ofthe sheath grabber is restricted by the interaction between the biasingmeans and the engaging means such that the grabber is biased to engagethe sheath and wherein movement of the cap relative to the sheathgrabber is restricted by the interaction between the second blockingmeans and the second stop means such that the cap, the grabber and thesheath can be removed from the device

According to yet another aspect of the invention the cap comprises anouter tubular member and an inner coaxial tubular member.

According to yet a further aspect of the invention, said outer tubularmember and said inner tubular member are integrally arranged, or joinedtogether, by a generally annular transversal wall, extending between theproximal ends of the inner and outer tubular members.

According to another aspect of the invention the sheath grabber iscoaxially and slidably arranged within the inner tubular member of thecap.

According to a further aspect of the invention said sheath grabberfurther comprises first stop means, and wherein said cap furthercomprises guide means and first blocking means arranged to said guidemeans.

According to yet another aspect of the invention said first stop meansis slidably arranged to said guide means and configured to interact withsaid first blocking means for holding the sheath grabber within the cap.

According to yet a further aspect of the invention said second stopmeans is a transversal member, wherein said engaging means comprises atleast two radially resilient flexible arms extending longitudinally fromsaid transversal member, and wherein said first stop means is a flexiblelatch member integral with, or attached to, the at least two radiallyresilient flexible arms.

According to another aspect of the invention each of the at least tworadially resilient flexible arms comprises hooks or radially inwardlydirected edges, grooves and/or protrusions for improving friction and/orconnection between the engaging means and the needle sheath.

According to a further aspect of the invention said second blockingmeans is at least two longitudinally extending ribs on the innercircumferential surface of said inner tubular member.

According to yet another aspect of the invention the guide means is atleast two longitudinally extending grooves or ridges on the innercircumferential surface of said inner tubular member and wherein thefirst blocking means is in the form of a distally directed surface or aledge arranged inside or integrally within each of the at least twolongitudinally extending grooves or ridges.

According to yet a further aspect of the invention the biasing means isconfigured as a number of radially protruding, longitudinally elongatedfins equally spaced around the inner circumferential surface of theinner tubular member, wherein the fins are ramp-shaped, such that thesloping edges of the fins slope from the inner surface of the innertubular member in a direction towards the distal end of said innertubular member.

According to another aspect of the invention the fins protrude up to apredetermined height at a predetermined distance from the distal end ofthe inner tubular member, and wherein said height and distance areadapted to the configuration of the engaging means for biasing saidengaging means radially inwards and thereby achieving a maximum engagingforce between the engaging means and the needle sheath when the cap iscoaxially movable relative to the sheath grabber.

According to a further aspect of the invention the second stop means ispositioned at a predetermined distance from the second blocking meanswhen the cap is attached to the device and wherein the second stop meansand the second blocking means abut each other when the cap is coaxiallymoved in relation to the grabber said predetermined distance such thatthe cap biases the sheath grabber to move axially.

The present invention has a number of advantages. The ability ofrelative movement between the cap and the sheath remover allows the gripon the sheath to be increasingly tightened as a user pulls the cap fromthe housing, up to a point where the cap starts to pull the sheathremover, and consequently the sheath, from the needle, at which pointthe grip is at its strongest. The sheath remover assembly will continueto grip the sheath throughout the removal process—actually even afterthe sheath has been completely removed.

Thus, since the gripping member and the cap are linked to each other andthe biasing member is also a part of the remover assembly the grippingforce will remain strong throughout the process. The remover assemblyalso does not risk getting stuck at the housing due to tolerancemismatch.

In addition, as the user pulls at the cap, the cap will first come loosefrom the housing. Then the cap will engage the sheath remover and thesheath to remove the latter from the needle. Consequently, the removalof cap and needle sheath is divided into two steps such that thefrictional force between the cap and the housing is overcome in thefirst step, followed by overcoming the frictional force between thesheath and the needle in the second step. Therefore the cap and theneedle sheath are easy to remove, even for users with weak hands or withimpaired manual dexterity.

Experiments have also shown that the sheath remover assembly is capableof removing a rigid needle shield (RNS) from a needle. A rigid needleshield is characterized in that the soft rubber sheath is surrounded bya rigid plastic or metal casing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description of embodiments of the invention, referencewill be made to the accompanying drawings of which:

FIG. 1 is a perspective view of an exemplary embodiment of the presentinvention when assembled to a medicament delivery device.

FIG. 2 is an exploded perspective view of an exemplary embodiment of thedevice shown in FIG. 1.

FIG. 3 is an exploded cross-section of an exemplary embodiment of thepresent invention.

FIG. 4A & 4B are cross-sections showing the working principle of thepresent invention.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described in detail. Asshould be noted in the present application, when the term “distalpart/end” is used, this refers to the part/end of the delivery device,or the parts/ends of the members thereof, which is/are located thefurthest away from the medicament delivery site of the patient.Correspondingly, when the term “proximal part/end” is used, this refersto the part/end of the delivery device, or the parts/ends of the membersthereof, which, is/are located closest to the medicament delivery siteof the patient.

According to a main aspect of the invention it relates to a needlesheath remover assembly for use in a medicament delivery device, axiallyelongated in a proximal and a distal direction, comprising a capconfigured to be removably attached to a housing of a medicamentdelivery device, a sheath grabber connected to said cap and configuredto be engageable to a needle sheath of a medicament container positionedwithin said medicament delivery device, wherein said cap and said sheathgrabber are axially movable in relation to each other and wherein saidsheath grabber and said cap are configured to interact with each othersuch that upon removal of said cap from the housing, said sheath grabberis capable of engaging and removing said needle sheath.

An exemplary embodiment of the present invention is shown in the FIGS.1-4. FIG. 1 is a perspective view of a medicament delivery device 30which is elongated along a longitudinal axis Z and has a proximal endand a distal end. In the text below, references will be made to thelongitudinal axis Z. Terms such as axial, axially, longitudinal,longitudinally, coaxial, along an axis or around an axis all refer tomovements and/or positions in relation to the longitudinal axis Z.

Also, when referring to a radial inward or radial outward direction, itis taken to mean a direction orthogonally towards or orthogonally awayfrom the longitudinal axis Z, respectively.

The exemplary delivery device of FIG. 1 is an auto injector, but couldin practice be any kind of delivery device having a needle sheath thathas to be removed prior to administration of its contents.

The figures show a soft needle sheath, e.g. rubber, but the sheath couldalso be a rigid needle shield (RNS), wherein a rigid casing, e.g.plastic or metal, fixedly surrounds a soft sheath.

The device shown in FIG. 1 comprises a housing 32 (FIG. 2) to whichproximal end is attached a sheath remover assembly according to thepresent invention. The sheath remover assembly comprises a cap 10,removably attached to the housing, and a sheath grabber 20. The cap 10and the sheath grabber 20 are mechanically connected but movable inrelation to each other along the longitudinal axis Z within certainlimits, as will be explained below.

FIG. 2 illustrates an exploded perspective view of the embodiment ofFIG. 1. The delivery device is shown to comprise a housing 32, anextendable needle guard 34, a container holder 36 and a power pack 38. Amedicament container 46, containing a medicament and a stopper 48, maybe accommodated in the container holder 36. A needle (not shown) isattached to a proximal end of the medicament container 46. The needle isin turn covered by a needle sheath 42. The needle sheath is preferablymade of a soft and resiliently flexible material, e.g. rubber.

Also illustrated in FIG. 2 is the sheath remover assembly, comprisingthe cap 10 and the sheath grabber 20. In FIG. 2 the cap and grabber areshown in an unassembled state. When the device is delivered to a user,the cap and grabber are assembled and attached to the proximal end ofthe housing 32, as shown in FIG. 1, such that the cap and the sheathgrabber may interact to engage and to remove the needle sheath 42 fromthe needle when the user removes the cap from the delivery device bypulling it proximally in relation to the housing, as will be explainedbelow.

FIG. 3 shows a detailed view of an exploded cross-section of the sheathremover assembly. The cap 10 comprises an outer tubular member 11 and aninner coaxial tubular member 12, which are integrally arranged, orjoined together, by a generally annular transversal wall 16, extendingbetween the proximal ends of the inner and outer tubular members. Thus,the proximal end of the inner tubular member 12 is open, such that itmay receive the sheath grabber 20 upon assembly of the cap and thesheath grabber. In FIG. 3, the annular transversal wall is substantiallydome-shaped, but could also be of any other shape without affecting thefunctionality of the current invention. When assembled, the sheathgrabber 20 is coaxially and slidably arranged within the inner tubularmember 12 of the cap.

In the exemplary embodiment, the inner circumferential surface of theinner tubular member 12 of the cap further comprises first blockingmeans 14, second blocking means 17 and biasing means 18, which areconfigured to interact with first stop means 21, second stop means 24and engaging means 22, respectively, comprised by the sheath grabber.

The first stop means 21 of the sheath grabber, in the exemplaryembodiment of FIG. 3, is in the form of latch members integral with, orattached to, a proximal part of the engaging means 22, such that saidlatch members are resiliently flexible in a radial direction butsubstantially rigid in a longitudinal direction. In the assembled devicethe first stop means 21 is slidably arranged to a guide means 15 andconfigured to interact with the first blocking means 14 for holding thesheath grabber 20 within the cap 10.

The second stop means 24 of the sheath grabber is a transversal memberand may be configured in the shape of a transversal wall part configuredsuch that said transversal wall part may be accommodated inside theinner tubular member 12 of the cap 10. The engaging means 22 extenddistally from a distal surface of said transversal wall part. Theengaging means 22 may, for instance, comprise at least two radiallyresilient flexible arms extending longitudinally from the transversalmember, equally spaced along a peripheral edge of the distal surface ofsaid first stop means 21 and configured to be resiliently flexible in aradial direction. The first stop means 21 may be flexible latch membersintegral with, or attached to, the at least two radially resilientflexible arms. A distal part of the engaging means 22 is arranged withgripping structures for improved friction between the engaging means andthe needle sheath 42 during a sheath removal operation. For instance,each of the at least two radially resilient flexible arms may comprisehooks or radially inwardly directed edges, grooves and/or protrusionsfor improving friction and/or connection between the engaging means andthe needle sheath 42.

The first blocking means 14 is arranged at a proximal end of a guidemeans 15. The first blocking means may be in the form of a distallydirected surface, e.g. a ledge, arranged inside or integrally within theguide means. The guide means may be configured as at least twolongitudinal grooves extending distally from the proximal end of the ofthe inner circumferential surface of the inner tubular member 12 suchthat the first stop means 21, e.g. the latch members, may be slidablyarranged within said grooves. It would also be possible to use ridges orribs instead of grooves. In such a case it would obviously be necessaryto also modify the latch members, the first blocking means and thesecond stop means to be able to interact with a ridge instead of agroove, but such modifications are well within the capability of askilled person.

When the cap and the sheath grabber are positioned in relation to eachother such that a proximally directed surface of the first stop means 21of the sheath grabber abuts the distally directed surface of the firstblocking means 14 of the cap, the sheath remover assembly is defined tobe in a first state.

The second blocking means 17 is also arranged on the innercircumferential surface of the inner tubular member 12, for instance inthe shape of at least two longitudinally extending ribs. A proximal endof the second blocking means is configured with a proximally directedledge at a predetermined distance from the proximal end of the innertubular member. When the cap and the sheath grabber are positioned inrelation to each other such that a distally directed surface of thesecond stop means 24 of the sheath grabber abuts the proximally directedledge of the second blocking means 17 of the cap, the sheath removerassembly is defined to be in a second state.

The cap is coaxially movable relative to the sheath grabber preferablywherein movement of the sheath grabber is restricted by the interactionbetween the biasing means 18 and the engaging means 22 such that thegrabber is biased to engage the sheath 42 and wherein movement of thecap relative to the sheath grabber is restricted by the interactionbetween the second blocking means 17 and the second stop means 24 suchthat the cap, the grabber and the sheath can be removed from the device

The second stop means 24 is positioned at a predetermined distance fromthe second blocking (17) means when the cap is attached to the devicesuch that the second stop means and the second blocking means abut eachother when the cap is coaxially moved in relation to the grabber saidpredetermined distance such that the cap biases the sheath grabber tomove axially.

The distal part of the inner tubular member 12 is arranged with biasingmeans 18. In the exemplary embodiment of FIG. 3 the biasing means isconfigured as a number of radially protruding, longitudinally elongatedfins, equally spaced along the inner circumferential surface of theinner tubular member. The fins are ramp-shaped, such that the slopingedges of the fins slope from the inner surface of the inner tubularmember in a direction towards the distal end of said inner tubularmember, up to a predetermined height at a predetermined distance fromthe distal end of the inner tubular member. Said height and distance areadapted to the configuration of the engaging means 22 for biasing saidengaging means radially inwards and thereby achieve a maximum engagingforce between the engaging means and the needle sheath 42 when the capis coaxially movable relative to the sheath grabber. The angle betweenthe sloping edges of the fins and the inner surface of the inner tubularmember is preferably less than 45 degrees.

The function of the shield remover assembly will now be described inconjunction with FIG. 4A and 4B. After manufacturing, the componentparts of the device are assembled. For the sheath remover assembly, thismeans inserting the sheath grabber 20 into the inner tubular member 12of the cap 10. The sheath grabber is aligned with the cap such that thefirst stop means 21 enter the guide means 15 by pushing the sheathgrabber distally in relation to the cap until the first stop means snappast the first blocking means 14. The cap and the sheath remover arethen mechanically connected and axially movable in relation to eachother between the first state and the second state as described above.The cap and the sheath remover are rotationally locked about the axis inrelation to each other since the first stop means 21 protrudes into thegroove of the guide means 15. In the first state the proximal surface ofthe second stop means 24 may be flush with the proximal surface of thecap as shown in FIG. 1.

When a medicament container 46 with a needle 44 and a needle sheath 42has been loaded into the delivery device 30 the sheath remover assemblymay be mounted on the delivery device such that the sheath removerassembly covers the needle sheath. During mounting, as the assembly ispushed distally in relation to the delivery device and the sheath, theengaging means 22 is forced slightly radially outwards by the needlesheath such that a slight pressure, i.e. friction or connection, isachieved between the engaging means and the needle sheath 42. Duringthis movement the first stop means 21 abuts the first blocking means 14.At the end of the mounting movement a distal part of the outer tubularmember 11 engages a proximal part of the housing 32 such that amechanical connection is established between the sheath remover assemblyand the housing. In the exemplary embodiment the connection isfrictional and may be broken by simply pulling the cap and the housingapart, but other forms of connections are conceivable, e.g. a threadedconnection or a bayonet coupling. It is important to note that, in thefirst state, a turning movement of the sheath remover assembly about theaxis would not turn the sheath since the grabber is not squeezing thesheath.

The medicament delivery device is thus delivered to the user with thesheath remover assembly mounted to the device in the first state asshown in FIG. 1 and FIG. 4A.

In order to prepare the device for administration of medicament the userhas to remove the needle sheath 42 from the needle 44. This isaccomplished by the user pulling at the cap 10 proximally in relation tothe housing 32. As the frictional force between the cap and the housingis overcome the cap starts to move proximally relative to the housing.

Initially, due to the slight friction/connection between the engagingmeans 22 and the needle sheath 42, the sheath grabber 20 is notdisplaced axially by the cap, but remains stationary relative to thehousing. When the biasing means 18 of the cap makes contact with theengaging means of the grabber, interaction between the biasing means andthe engaging means therefore wedges the engaging means between thebiasing means and the needle sheath and forces the flexible engagingmeans radially inwards, increasing the radial pressure on the needlesheath for engaging it. In the exemplary embodiment, this is illustratedby the arms of the engaging means climbing up the ramps of the biasingmeans, while at the same time the gripping structures of the engagingmeans dig into the relatively soft rubber material of the needle sheath.

As the sheath remover assembly reaches the second state the second stopmeans 24 is brought into abutment with the second blocking means 17. Atthis point the engaging means has reached a maximum engagement with theneedle sheath. This is exemplified by the gripping structures of theengaging means in FIG. 4B being aligned with the predetermined maximumheight of the fins. Since the second stop means and the second blockingmeans abut each other the cap and the sheath grabber are now stationaryin relation to each other.

Hypothetically, if the biasing means was allowed to pass the grippingstructures of the exemplary embodiment the arms of the engaging meanswould risk flexing radially outwards again, thereby decreasing the gripon the needle sheath. Therefore the maximum height of the biasing meansis arranged at a predetermined distance from the proximal end of thesecond blocking means 17 equal to the longitudinal length of theengaging means, such that the exemplary gripping structures come to restat a maximum engagement with the needle sheath in the second state ofthe sheath remover assembly.

Accordingly, as the user continues to pull at the cap, interactionbetween the second stop means and the second blocking means forces thesheath remover assembly to continue movement as a unit, i.e. the sheathgrabber starts to move together with the cap relative to the deliverydevice. Since the engagement between the sheath grabber and the needlesheath is strong at this point, the needle sheath is forced to movealong together with the sheath remover assembly. As the needle sheath isremoved from the needle, the device is ready for administration ofmedicament.

In other words, the cap is coaxially movable relative to the sheathgrabber in a proximal direction, whereas the movement of the sheathgrabber is restricted by the interaction between the biasing means andthe engaging means such that the grabber is biased to engage the sheathand movement of the cap relative to the sheath grabber is restricted bythe interaction between the second blocking means and the second stopmeans such that the cap, the grabber and the sheath can be removed fromthe device when pulled in a proximal direction.

The second stop means is positioned at a predetermined distance from thesecond blocking means when the cap is attached to the device so that thesecond stop means and the second blocking means abut each other when thecap is coaxially moved proximally in relation to the grabber saidpredetermined distance such that the cap biases the sheath grabber tomove axially in the proximal direction. While the invention has beenillustrated and described in detail in the drawings and foregoingdescription, such illustration and description are to be consideredillustrative or exemplary and not restrictive. It will be understoodthat changes and modifications may be made by those of ordinary skillwithin the scope of the following claims. In particular, the presentinvention covers further embodiments with any combination of featuresfrom different embodiments described above and below.

Furthermore, in the claims the word “comprising” does not exclude otherelements or steps, and the indefinite article “a” or “an” does notexclude a plurality. A single unit may fulfil the functions of severalfeatures recited in the claims. The terms “essentially”, “about”,“approximately” and the like in connection with an attribute or a valueparticularly also define exactly the attribute or exactly the value,respectively.

Any reference signs in the claims should not be construed as limitingthe scope.

The invention claimed is:
 1. A needle sheath remover assembly for amedicament delivery device, comprising: a cap configured to mechanicallyconnect to a housing of the medicament delivery device, wherein theneedle sheath remover assembly is mounted to the medicament deliverydevice in a first state; a sheath grabber connected to the cap andconfigured for engaging a needle sheath of a medicament container in themedicament delivery device when the needle sheath assembly is in asecond state; wherein the cap is moveable in a proximal direction withrespect to the sheath grabber between the first state, wherein thesheath grabber is not engaging the needle sheath, and the second state;and wherein the cap and the sheath grabber are configured forinteraction with each other such that upon mechanically disconnectingthe cap from the housing of the medicament delivery device, the sheathgrabber is able to engage and remove the needle sheath.
 2. The needlesheath remover assembly of claim 1, wherein the sheath grabber comprisesa second stop device and an engaging device.
 3. The needle sheathremover assembly of claim 2, wherein the cap comprises a second blockingdevice and a biasing device.
 4. The needle sheath remover assembly ofclaim 3, wherein movement of the sheath grabber is restricted byinteraction between the biasing device and the engaging device such thatthe sheath grabber is biased to engage the sheath.
 5. The needle sheathremover assembly of claim 4, wherein movement of the cap relative to thesheath grabber is restricted by interaction between the second blockingdevice and the second stop device such that the cap, the sheath grabber,and the needle sheath can be removed from the medicament deliverydevice.
 6. The needle sheath remover assembly of claim 3, wherein thesecond blocking device includes at least two longitudinally extendingribs on an inner circumferential surface of the inner tubular member. 7.The needle sheath remover assembly of claim 3, wherein the biasingdevice includes a plurality of radially protruding, longitudinallyelongated fins spaced around an inner circumferential surface of theinner tubular member.
 8. The needle sheath remover assembly of claim 7,wherein the fins comprise ramp-shaped such that edges of the fins slopefrom the inner circumferential surface toward a distal end of the innertubular member.
 9. The needle sheath remover assembly of claim 7,wherein the fins protrude up to a predetermined height at apredetermined distance from the distal end of the inner coaxial tubularmember, and the height and distance are adapted to the engaging devicefor biasing the engaging device radially inward and enhancing anengaging force between the engaging device and the needle sheath whenthe cap is coaxially moved relative to the sheath grabber.
 10. Theneedle sheath remover assembly of claim 3, wherein the second stopdevice is at a predetermined distance from the second blocking devicewhen the cap is attached to the medicament delivery device.
 11. Theneedle sheath remover assembly of claim 10, wherein the second stopdevice and the second blocking device abut each other when the cap iscoaxially moved in relation to the sheath grabber the predetermineddistance such that the cap biases the sheath grabber to move axially.12. The needle sheath remover assembly of claim 2, wherein the secondstop device includes a transversal member, the engaging device comprisesat least two radially resilient flexible arms extending longitudinallyfrom the transversal member.
 13. The needle sheath remover assembly ofclaim 1, wherein the cap comprises an outer tubular member and an innertubular member.
 14. The needle sheath remover assembly of claim 13,wherein the outer tubular member and the inner tubular member areintegral.
 15. The needle sheath remover assembly of claim 13, whereinthe outer tubular member and the inner tubular member are joinedtogether by a generally annular transversal wall that extends betweenproximal ends of the inner and outer tubular members.
 16. The needlesheath remover assembly of claim 13, wherein the sheath grabber isslidably arranged within the inner tubular member.
 17. The needle sheathremover assembly of claim 13, wherein a distal part of the outer tubularmember engages a proximal part of the housing of the medical deliverydevice such that a mechanical connection is established between thesheath remover assembly and the housing.
 18. The needle sheath removerassembly of claim 13, wherein the sheath grabber further comprises afirst stop device, and the cap further comprises a guide and a firstblocking device arranged to the guide.
 19. The needle sheath removerassembly of claim 18, wherein the first stop device is slidably arrangedto the guide and is configured for interaction with the first blockingdevice for holding the sheath grabber in the cap.
 20. The needle sheathremover assembly of claim 18, wherein the first stop device comprises atleast one flexible latch member integral with the at least two radiallyresilient flexible arms.
 21. The needle sheath remover assembly of claim20, wherein the at least two radially resilient flexible arms comprise ahook for connection between the engaging device and the needle sheath.22. The needle sheath remover assembly of claim 18, wherein the guideincludes at least two longitudinally extending grooves or ridges on aninner circumferential surface of the inner tubular member.
 23. Theneedle sheath remover assembly of claim 22, wherein the first blockingdevice comprises a distally directed surface arranged inside each of theat least two longitudinally extending grooves or ridges.
 24. The needlesheath remover assembly of claim 1, wherein the cap comprises a frictionfit that mechanically connects the cap to the housing of the medicamentdelivery device.
 25. The needle sheath remover assembly of claim 1,wherein the cap comprises a thread that mechanically connects the cap tothe housing of the medicament delivery device.
 26. The needle sheathremover assembly of claim 1, wherein the cap comprises a bayonet thatmechanically connects the cap to the housing of the medicament deliverydevice.